Dermal heatsink exhibiting hydrophilic and contaminant resistant properties and method for fabricating a dermal heatsink

ABSTRACT

One variation of a method for fabricating a dermal heatsink includes: fabricating a substrate defining an interior surface, an exterior surface opposite the interior surface, and an open network of pores extending between the interior surface and the exterior surface; activating surfaces of the substrate and walls of the open network of pores; applying a coating over the substrate to form a heatsink, the coating comprising a porous, hydrophilic material and defining a void network; removing an excess of the coating from the substrate to clear blockages within the open network of pores by the coating; hydrating the heatsink during a curing period; heating the heatsink during the curing period to increase porosity of the coating applied over surfaces of the substrate; and rinsing the heatsink with an acid to decarbonate the coating along walls of the open network of pores in the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/574,048, filed on 17 Sep. 2019, which claims the benefit of U.S.Provisional Application No. 62/732,193, filed on 17 Sep. 2018, each ofwhich is incorporated in its entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the field of heat transfer and morespecifically to a new and useful dermal heatsink and a method forfabricating the dermal heatsink in the field of heat transfer.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are schematic representations of a dermal heatsink;

FIGS. 2A and 2B are schematic representations of the dermal heatsink;

FIGS. 3A, 3B, 3C, and 3D are schematic representations of variations ofthe dermal heatsink; and

FIGS. 4A, 4B, and 4C are a flowchart representation of a method.

DESCRIPTION OF THE EMBODIMENTS

The following description of embodiments of the invention is notintended to limit the invention to these embodiments but rather toenable a person skilled in the art to make and use this invention.Variations, configurations, implementations, example implementations,and examples described herein are optional and are not exclusive to thevariations, configurations, implementations, example implementations,and examples they describe. The invention described herein can includeany and all permutations of these variations, configurations,implementations, example implementations, and examples.

1. Apparatus

As shown in FIGS. 1A, 1B, 2A and 2B, a dermal heatsink 100 includes aheatsink 102 including a substrate 110 that defines: an interior surface114 configured to thermally couple to a heat source 150; an exteriorsurface 116; and an open network of pores 112 extending between theinterior surface 114 and the exterior surface 116. The heatsink 102 alsoincludes a coating 120: defining a porous, hydrophilic material;defining a void network 121 configured to filter hydrophobic molecules;extending across the interior surface 14 of the substrate 110; andlining the open network of pores 112 within the substrate 110. Thesubstrate 110 and the coating 120 of the heatsink 102 cooperate to wickmoisture from a surface of the heat source 150, through the void network121 lining the open network of pores 112, to the exterior surface 116.

2. Method

As shown in FIGS. 4A and 4B, a method S100 for fabricating ahydrophilic, contaminant resistant dermal heatsink 100 includes:fabricating a substrate 110 defining an interior surface 114, anexterior surface 116, and an open network of pores 112 extending betweenthe interior surface and the exterior surface in Block S110; activatingsurfaces of the substrate 110 and walls of the open network of pores 112in Block S120; applying a coating 120 over the substrate 110 to form aheatsink 102 in Block S130, the coating 120 comprising a poroushydrophilic material; removing an excess of the coating 120 from thesubstrate 110 to clear blockages within the open network of pores 112 bythe coating 120 in Block S140; hydrating the heatsink 102 during acuring period in Block S150; heating the heatsink 102 during the curingperiod in Block S150 to increase porosity of the coating 120 appliedover surfaces of the substrate 110; and rinsing the heatsink 102 with anacid to decarbonate the coating 120 along walls of the open network ofpores 112 in the substrate 110 in Block S155.

As shown in FIG. 4C one variation of the method S100 further includes:forming a first aperture 132 in a textile panel 130 in Block S160;locating the heatsink 102 within the first aperture 132 in the textilepanel 130; locating a heatsink retainer 140 about a periphery of thefirst aperture 132 in the textile panel 130, the heatsink retainer 140defining a set of claws 142 extending over channels defined by theheatsink 102; and bonding the heatsink retainer 140 to the textile panel130 about a periphery of the first aperture 132 in Block S170, the setof claws 142 securing the heatsink 102 within the first aperture 132.

3. Applications

The method S100 can be executed to fabricate a heatsink 102 thatincludes: a substrate 110 defining an open network of pores 112 (or“open-celled pores” or “channels”); and a coating 120 of a poroushydrophilic material that lines internal and external surfaces of thesubstrate 110—including walls of the open network of pores 112 in thesubstrate. The coating 120 can form a robust shell around the substrateand can function to wick moisture from a contact surface 126 at one sideof the heatsink 102 in contact with a human user's skin, transport thismoisture through the open network of pores 112 in the substrate (e.g.,via capillary action), and raise this moisture to an evaporative surface128 defined by surfaces of the coating 120 at an opposite side of theheatsink 102 and within the internal network of pores 112. Theevaporative surface 128 can span a set of fins across the heatsink 102and may be cooled via evaporative cooling as moisture—drawn from thecontact surface 126 through the void network 121 of the coating 120lining the open network of pores in the substrate 110—evaporates.Accordingly, the substrate 110 draws heat from the user's skin at thecontact surface 126 and conducts this heat to the evaporative surface128, which releases this heat to the environment (e.g., via convectionand radiation), thereby cooling the user. In particular, the method S100can be executed to fabricate a heatsink 102 that includes a conductive,porous substrate 110 lined with a hydrophilic, porous coating 120 suchthat the heatsink 102: defines a dense open network of pores 112 withsufficient pore size such that air may flow freely through pores and theavailable surface area for application of the coating 120 is increased.The coating 120 defines a void network 121 (or “porous microstructure”)with minimal void (or “pore”) size exhibiting low resistance totransport of moisture (e.g., high permeability to water) between thecontact surface 126 (adjacent the interior surface 114 of the substrate110) and surfaces of the coating 120 within the open network of pores112 and the evaporative surface 128 (adjacent the external surface ofthe substrate 110), and exhibits high resistance to transport of otherorganic molecules (e.g., oils) through the void network 121. Forexample, the dense open network of pores 112 defined by the heatsink 102can exhibit pore sizes large enough to be lined by the coating 120 andfor effective flow of air through pores in the open network of pores112, and the coating 120 can be processed such that at room temperatureconditions, the void network 121 of the coating 120 is hydrated (e.g.,the pores are filled with water molecules) and therefore hydrophilic(e.g., attracted to water molecules) and contaminant resistant due tothe size of pores in this void network 121 (e.g., larger hydrophobicmolecules cannot displace the smaller water molecules present in thesehydrated pores). The heatsink 102 may therefore be hydrophilic andexhibit contaminant resistant properties (e.g., contaminant resistant)properties due to the hydrated void network 121 of the coating 120lining the open network of pores 112.

The resulting heatsink 102 can thus define: a porous,thermally-conductive structure (i.e., the substrate 110) with a networkof interconnected pores encased in a rigid, hydrophilic shell (i.e., thecoating 120) that exhibits greater affinity to polar substances (e.g.,water) than to non-polar substance (e.g., oil). The coating 120 thusforms hydrophilic surfaces that are resistant to hydrophobiccontaminants, such as volatile organic compounds (VOCs) and oils; byspanning interior and exterior surfaces of the substrate 110, thecoating 120 thus increases hydrophilicity and increases resistance ofthe heatsink 102. More specifically, this greater affinity of thecoating 120 to polar substances enables water to wet surfaces of theheatsink 102 when oils and other contaminants are present at thesesurfaces, such as at the contact surface 126 when the contact surface126 is placed in contact with a user's forehead, forearm, or chest.Additionally, because the coating 120 exhibits a relatively highaffinity to polar substances, the heatsink 120 may be quickly cleaned ofoils and other contaminants by rinsing with water and/or surfactants(e.g., soap). Therefore, a heatsink 102 defining a durable, contaminantresistant wicking structure (e.g., heatsink) exhibiting hydrophilicity,contaminant resistance, and high thermal conductivity can be fabricatedaccording to Blocks of the method S100.

In one variation, the heatsink 102 can be incorporated into a textile orwearable article of clothing to form a wearable dermal heatsink 100. Forexample, the heatsink 102 can be mounted or adhered over a bore (or an“open”) defined in a forehead area of a headband, in a chest area of ashirt, in a torso area of a vest, or in a forearm area of an armband orwristband. In particular, the heatsink 102 can be mounted or coupled tothe textile such that the contact surface 126 of the heatsink 102contacts skin of the user when the dermal heatsink 100 is worn by auser. Furthermore, multiple instances of the heatsink 102 can beincorporated into the dermal heatsink 100 in order to achieve contactbetween contact surfaces 126 of units of the heatsink 102 while enablingthe dermal heatsink 100 to conform to the user's (unique) body (e.g.,forehead, abdomen) geometry during use.

A user may therefore wear the dermal heatsink 100—including one ormultiple instances of the heatsink 102 arranged over corresponding boresin the dermal heatsink 100—to wick moisture (i.e., sweat) from regionsof her skin in contact with these heatsinks 102 and to cool (e.g., viaevaporative cooling) these regions of her body. In particular, aheatsink 102 integrated into the dermal heatsink 100 a) defines anevaporative surface 128 that defines a larger surface area than the areaof the user's skin in contact with the contact surface 126 of theheatsink 102 and b) absorbs heat from the user via the contact surface126, thereby increasing an effective surface area of the user's skin. Byabsorbing moisture (e.g., sweat) from the user's skin and transportingthis moisture from the contact surface 126 to the evaporative surface128—defined by coating-air interfaces including surfaces of an interiorshell of the coating 120 lining the open network of pores 112 and of anexterior shell of the coating 120 lining the exterior surface of thesubstrate—the heatsink increases a rate of evaporative cooling acrossthe larger surface area of the evaporative surface 128 and internalcoating 120 surfaces, thereby increasing a rate of heat transfer out ofthe adjacent region of the user's skin and increasing a rate of coolingof the user's body. Furthermore, because the heatsink 102 exhibitscontaminant resistance, the heatsink may exhibit low propensity toabsorb oil from the user's skin, thereby limiting uptake of oils fromthe user's skin, limiting fouling by natural oils produced by the user,maintaining high permeability of water (e.g., sweat) from the user'sskin, and maintaining a high rate of evaporative cooling even duringextended periods of use by the user.

A user may wear the dermal heatsink 100 on regions of the skincorresponding a high density of blood vessels to increase total bodycooling, and/or on regions of the skin where a body may produce heat ata higher rate (e.g., a human forehead). For example, a set of heatsinks102 can be incorporated into a textile panel 130 to define a dermalheatsink 100 in the form of a headband. A user may wear this headbandwhile running a marathon (e.g., over two hours) or cycling a centuryride (e.g., over seven hours) to extract heat from the user's head andcool the user more generally at a rate: proportional to the user's sweatrate; proportional to the user's speed (which affects a rate of airflowover the heatsink 102); and therefore approximately proportional to theuser's power output during exercise.

In another example, a set of heatsinks 102 are incorporated into atextile panel 130 to define a dermal heatsink 100 in the form of a vest.In this example, rather than immerse a hyperthermic patient in an icebath or spray a mist at the hyperthermic patient, medical staff maydouse the vest with water, place the vest on a hyperthermic patient, andplace the patient near a fan in order to consistently extract heat at ahigh rate from the patient's torso. In particular, when paired with afan, the wetted vest may achieve a high rate of cooling for thehyperthermic patient in a wide variety of environments: with minimalsetup time (e.g., compared to an ice bath or mist system); withoutrisking tissue damage from prolonged contact with chilled fluid; withoutnecessitating consumption of a large volume of water; withoutsubstantively increasing local humidity (e.g., compared to a mist);without producing a spill hazard from a liquid spill; and at a rate moreisolated from ambient wind and temperature conditions than a mistsystem.

4. Terms

As described above, the coating 120 defines a hydrophilic cementitiousmixture lining surfaces of the substrate 110 and walls of the network ofpores 112 such that the formed heatsink exhibits hydrophilic behaviorenabling the flow of moisture (e.g., water) through the void network 121of the coating 120 lining the open network of pores 112 within theheatsink 102, the interior surface 114 and the exterior surface 116.Additionally, the coating 120 functions as a hydrophilic layer over thesubstrate 110, such that water may flow freely through the substrate 110from the contact surface 126 of the coating 120 to the evaporativesurface 128 of the coating 120 and displace oils and/or otherhydrophobic contaminants clogging the open network of pores 112.

The coating 120 exhibits a greater affinity to polar substances (e.g.,water) than to nonpolar substances (e.g., oil). This higher affinity topolar substances enables moisture to wet the coating 120 and thereforesurfaces of the heatsink 102. Additionally, because the coating 120exhibits a higher affinity to water than oils and other contaminants, inthe presence of both, the coating 120 can interact with water moleculesrather than the oil molecules, thus exhibiting contaminant resistanttendencies. Furthermore, when oils are present on surfaces of theheatsink 102, water in sweat or from an external source can more readilydisplace these oils from surfaces of the heatsink 102.

The substrate 110 defines an open network of pores 112 extending betweenan interior surface 114 of the substrate 110 and an exterior surface 116of the substrate 110. The network of pores 112 includes open-cell poresthat can extend from the interior surface 114 to the exterior surface116. The substrate 110 can define this network of pores 112 atsubstantially uniform density throughout its volume. The sizes of poresin the open network of pores 112 are sufficiently large such that airand moisture may flow through the open network of pores 112. At thesesizes, oils and other contaminants may enter and/or clog the opennetwork of pores. Therefore, the coating 120 interacts with surfaces ofthe open network of pores 112 to form a hydrophilic layer lining thesesurfaces, such that water may flow through the open network of pores 112and displace contaminants. Therefore, the heatsink 102 is contaminantresistant in that the interactions between the network of pores 112within the substrate 110 and the void network 121 of the coating 120increases hydrophilic tendencies (e.g., increases an affinity for watermolecules) and reduces hydrophobic interactions (e.g., lowers anaffinity for hydrophobic molecules).

5. Example

In one implementation, the dermal heatsink 100 is a headband 160configured to be worn by a user about her forehead as shown in FIGS. 2A,2B, and 3A. The headband 160 can be worn during exercise by the user towick sweat from the forehead of the user and to cool the user as a bodytemperature of the user increases during exercise. As shown in FIGS. 2A,2B, and 3A, the headband 160 includes: a set of heatsinks 102, eachheatsink in the set of heatsinks 102 configured to wick moisture fromthe forehead of the user and to cool a temperature of the user; and atextile panel 130 in which the set of heatsinks 102 are arranged, suchthat when the textile panel 130 is attached to the forehead of the user,the set of heatsinks 102 contact skin of the user.

Each heatsink can define: a substrate 110 machined from athermally-conductive graphite foam and defining an open network of poresextending between surfaces of the substrate 110; and a hydrophilic,contaminant resistant coating defining a cementitious mixture andextending across surfaces of the substrate 110 and lining the opennetwork of pores 112 within the substrate 110. Therefore, the heatsink102 exhibits high thermal conductivity and is sufficiently hydrophilicsuch that the heatsink 102 can dissipate heat from the body of the userand wick moisture (e.g., water in sweat of the user) through the opennetwork of pores 112. Each heatsink can include a set of fins 9configured to increase heat dissipation by increasing surface area ofthe heatsink 102. For example, the substrate 110 can further define: abase 118 defining an interior surface 114 of the substrate 110; and aset of fins 9 extending from the base 118 opposite the interior surface114 and defining an exterior surface 116 of the substrate 110.

In this implementation, each heatsink is attached to a textile panel 130configured to be worn on the forehead of the user. For example, theheadband 160 can include a textile panel 130 defining an aperture inwhich a heatsink 102 is arranged. The heatsink 102 is arranged in theaperture and attached to the textile panel 130 via a heatsink retainer140 encircling the conductive substrate. The heatsink retainer 140 canbe a square shaped, thermoplastic polymer and is configured to improvethe mechanical properties and attachment of the conductive heatsink tothe textile. The heatsink retainer 140 can adhere to the textile panel130 via partially melting or injecting the frame into the textile panel130 and the thermally conductive heatsink. In one variation, a firstheatsink retainer 140 is attached to the textile panel 130 about aperiphery of an aperture defined by the textile panel 130. After thefirst heatsink retainer 140 is attached to the textile panel 130, theheatsink 102 can be arranged in the aperture. Then, a second heatsinkretainer 140 can be melted or injected into the textile panel 130 andthe heatsink 102 to secure the heatsink 102 within the aperture of thetextile panel 130. Additionally, the heatsink retainer 140 can define aset of claws 142 that further secure the heatsink 102 within theaperture of the textile panel 130 and secure attachment of the heatsink102 to the retainer 140 during the melting or injection process. Forexample, the heatsink retainer 140 can define a set of claws that extendbetween fins of the heatsink 102 to further secure the heatsink 102 onthe textile panel 130.

The headband 160 can be manufactured to include a set of apertures(e.g., via laser cutting or mechanical cutting), each aperture in theset of apertures configured to fit a heatsink 102. For example, thetextile panel 130 can include a set of ten heatsinks 102 arranged intotwo symmetrical rows of heatsinks 102. The textile panel 130 includingthe heatsinks 102 can be incorporated (e.g., via sewing techniques) intoa wearable headband 160. When a user wears the headband 160 across herforehead, gaps between heatsinks 102 on the textile panel 130 enable thetextile panel 130 to conform to a curvature or shape of her forehead. Inone variation, as shown in FIG. 2, the heatsinks 102 are arranged in aVoronoi pattern on the textile panel 130, such that the heatsinks 102vary in size and shape to account for the natural shape of a humanforehead. Alternatively, the headband 160 can include heatsinks 102 witha particular shape and size and arranged in a particular geometryaccording to the curvature and forehead shape of a particular user.

As shown in FIG. 3A, a user may wear the headband 160 across herforehead when exercising to wick sweat from her body and cool her bodytemperature. The user may wear the headband 160 with the interiorsurface 114 of the substrate 11 in contact with skin (e.g., on theforehead) of the user. The hydrophilic, contaminant resistant coating ofthe heatsink 102 enables moisture (e.g., sweat) on the forehead of theuser to be absorbed by the interior surface 114 of the substrate 110,pass through the network of pores within the substrate 110, and exit tothe evaporative surface 128 of the coating 120, lining the exteriorsurface 116 of the substrate 110 interior surfaces of the coating 120within the network of pores 112, where the moisture evaporates.

The heatsink 102 dissipates heat from the user via evaporation ofmoisture present at the surface of the coating 120. Therefore, when auser initially wears the dermal heatsink 100, a rate of heat transfermay be low as little to no moisture has been absorbed by the heatsink102. To increase the initial rate of heat transfer, a user may moistenor drench the dermal heatsink 100 with liquid before and/or duringphysical activity to activate the heatsink 102 such that heat transferfrom the user to the heatsink 102 begins immediately when the userbegins a physical activity and continues throughout performance of thephysical activity. A user may drench the apparatus with water from anexternal source such as a hose. Alternatively, in one variation, theapparatus can include a wearable tank that can administer liquid to theheatsinks 102.

As maximum heat transfer occurs when air flows through the apparatus(e.g., via increased evaporation and heat exchange via convection), thedermal heatsink 100 can operate at different rates of cooling based onair flow rates and angles of the airflow at which airflow contacts theheatsinks 102. Therefore, a user may experience different rates ofcooling depending on weather, physical activity, and motion of the user.For example, a first user biking outdoors with natural airflow mayexperience a greater cooling effect than a second user exercising on astationary bike indoors. To increase the cooling effect, the second userexercising indoors on the stationary bike may locate a fan in front ofthe stationary bike to simulate natural airflow and thus achieve asimilar cooling effect as the first user biking outdoors. In onevariation, to increase airflow through the heatsink 102, the heatsink102 can exhibit a geometry such that vortices are formed on the exteriorsurface 114 of the heatsink 102, thereby increasing airflow and reducingdrag.

6. Substrate

Generally, the heatsink 102 includes a substrate 110 defining: aninterior surface 114 configured to thermally couple to a heat source150; an exterior surface 116; and an open network of pores extendingbetween the interior surface 114 and the exterior surface 116. Morespecifically, the substrate 110 exhibits a particular geometry includinga fin side defining the exterior surface 116, and a body side definingthe interior surface 114. The substrate 110 is lined with a porous,hydrophilic coating to form the heatsink 102. The substrate 110 furtherdefines: a base 118 defining the interior surface 114, the base 118exhibiting a first surface area; and a set of fins 119 extending fromthe base 118 opposite the interior surface 114, the set of fins 119exhibiting a second surface area greater than the first surface area anddefining the exterior surface 116.

The substrate 110 exhibits a high thermal conductivity and is configuredto dissipate heat from a heat source 150 (e.g., transfer heat from aheat source 150 to the exterior surface 116 of the substrate 110). Theinterior surface 114 of the substrate 110 is configured to thermallycouple to the heat source 150 to enable heat dissipation from thesmaller surface area of the interior surface 114 to the greater surfacearea of the evaporative surface 128, defined by the surface area of theexterior surface 116 (e.g., the fins of the substrate 110) and thesurface area of the walls of the network of pores 112. A coatingdeposited over surfaces of the substrate 110 to increase hydrophilicityof the heatsink 102 may exhibit decreased thermal conductivity of theheatsink 102. Therefore, a material exhibiting high thermal conductivitycan be machined or molded to form the substrate 110 in order to maximizethe thermal conductivity of the heatsink 102 after addition of thecoating 120 to surfaces of the substrate 110.

The thermally conductive substrate can exhibit a porous structure anddefine an open network of pores, through which moisture can flow fromthe interior surface 114 of the substrate 110 to the exterior surface116 of the substrate 110. These pores exhibit sufficiently small volumessuch that moisture can be absorbed through the pores via capillaryaction, while larger molecules contained in oils and other contaminantscannot travel through the pores.

For example, the substrate 110 can define an open network of poresincluding pores exhibiting pore diameters between 275-microns and325-microns such that sufficient capillary pressure is generated forwater to flow through the open network of pores 112. In a similarexample, the substrate 110 defines the open network of pores 112exhibiting a pore size less than 400 microns, and the coating 120defines a thickness between 50 microns and 200 microns to yield aneffective pore size less than 100 microns on walls of the open networkof pores 112 in the substrate 110. The substrate 110 and the coating120—in the completed heatsink 102—can therefore cooperate to wickmoisture (e.g., sweat) from the interior surface to the exterior surfacevia the open network of pores 112 (e.g., via capillary action) when theheatsink 102 is in contact with a user's skin.

Additionally, the substrate 110 may exhibit higher mechanical durabilitywith decreased pore size. Therefore, the substrate 110 can include moreintricate base and fin features which may increase a rate of heatdissipation from a heat source 150 to the heatsink 102.

The substrate can be formed from a thermally conductive foam such as:aluminum foam, copper foam, or graphite foam. These foams exhibit porousstructures and therefore exhibit relatively high specific surface areas(e.g., surface area per volume). Thermally conductive foams also exhibitrelatively lower density than traditional metals included in heat sinks,due to their porous structure.

In one implementation, the substrate 110 is machined from a thermallyconductive graphite material defining an open network of pores. Theconductive graphite material can be a graphite foam (e.g., Graphite Foamproduced by C-FOAM Corporation of Western Australia). For example, thesubstrate 110 can be machined from a block of graphite foam, thegraphite foam exhibiting high thermal conductivity and low density.Generally, graphite foams can be made by: selecting a mold configured toshape the graphite foam and applying a mold release agent to walls ofthe mold; introducing a quantity of pitch to the mold; purging the moldof air via applying a vacuum or introducing an inert fluid; heating thepitch in the mold to a sufficient temperature such that the pitchcoalesces into a liquid (e.g., between 50° Celsius and 100° Celsiushigher than the softening point of the pitch); releasing the vacuum andapplying an inert fluid at a static pressure (e.g., approximately1000-psi); further heating the pitch to a high temperature such thatgases evolve and foam the pitch; and further heating the pitch to ahigher temperature to coke the pitch before cooling the pitch to roomtemperature, while gradually releasing the applied static pressure. Theresulting porous graphite foam may be machined to form the substrate110.

In one implementation, the substrate 110 is molded from a metallicmaterial, such as aluminum or copper. In this implementation, thesubstrate 110 can be molded to fit a particular size and geometry.

The substrate 110 can be machined to a particular shape and size. In onevariation, the substrate 110 exhibits a quadrangular prism shape anddefines straight, narrow channels on an upper section of the substrate110 to form a set of fins 9. The substrate 110 can include the set offins 119 to increase a surface area of the exterior surface 116, andtherefore increase the rate of heat dissipation from a heat source 150.The interior surface 114 of the substrate 110 can be straight or curvedto match a shape of regions of the human body. For example, the interiorsurface 114 of a substrate 110 may be curved to fit the curvature of aforehead of user. Alternatively, the interior surface 114 of thesubstrate 110 may be flat (e.g., straight edges) and include gapsbetween heatsinks 102 to enable bending or greater flexibility of thedermal heatsink 100 about regions of the body such that the dermalheatsink 100 can be worn by different users and conform to each useraccordingly.

7. Coating

As shown in FIGS. 1A and 1B, the heatsink 102 includes a coating 120lining each surface of the substrate 110 and the walls of pores in thenetworks of pores within the substrate 110. The coating 120 forms: aninterior shell 122 extending across the interior surface 114 of thesubstrate 110 and defining a contact surface 126 configured to contactskin of a user, the contact surface 126 defining a first area; and anexterior shell 124 extending across the exterior surface 116 of thesubstrate 110 and defining an evaporative surface 128 of a second areagreater than the first area.

Generally, the coating 120 functions as a hydrophilic shell cooperatingwith the substrate 110 to enable moisture wicking from skin of a useracross a contact surface 126 of the coating 120, through the opennetwork of pores 112 of the substrate 110, and across an evaporativesurface 128 of the coating 120, and to provide durability to theheatsink 102 structure. The coating 120 can define a cementitiousmixture exhibiting high water concentration such that the watermolecules in the coating 120 attract water molecules in moisture passingthrough the open network of pores 112 within the substrate 110,therefore exhibiting hydrophilic properties. The coating 120 alsofunctions as a contaminant resistant layer to prevent contaminants suchas oils from clogging the open network of pores 112.

The coating 120 can define a thin shell of approximately uniformthickness that: extends across the exterior surface 116 of the substrate110; extends across the interior surface 114 of the substrate 110; andlines the walls of the open network of pores 112 within the substrate110. In particular, the coating 120 can be of at least a minimumthickness across the surfaces of the substrate 110 in order to increasedurability of the heatsink 102 and increase resistance of the heatsink102 to oils and other contaminants. The coating 120 can be less than amaximum thickness in order to maintain the open network of pores 112within the substrate 110 and preserve the heat exchanger properties ofthe structure provided by the substrate 110, as the coating 120 is lessthermally conductive than the substrate 110. For example, the heatsink102 can include a substrate 110 machined from a graphite foam materialand exhibiting a first impact resistance. The heatsink 102 can alsoinclude a coating: defining a cementitious matrix and exhibiting asecond impact resistance greater than the first impact resistance, suchthat coating increases a durability of the heatsink 102; and exhibitinga thickness between 75-microns and 125-microns.

In one implementation, the coating 120 is a cementitious mixture ofdistilled water and cement (e.g., Portland white cement). To prepare thecoating 120 for application onto the substrate 110, a volume of water ismixed with a volume of cement (and an aggregate) at a water-cement ratiothat—when cured—yields a heterogeneous microstructure including a porestructure, cement, and interfacial transition zone that are permeable towater. More specifically, the coating 120 can harden as a result of achemical reaction between water and cement in this cementitious mixture.At a low water-cement ratio (e.g., less than 0.4), this reaction in thecoating 120 is fully hydrated but may exhibit a water permeabilityinsufficient to wet and fully coat the substrate 110. Further, at lowand moderate water-cement ratios (e.g., 0.35 to 0.65), the coating 120may exhibit minimal porosity, exhibit a network of narrow pores, andthus exhibit relatively low permeability to water when cured. Therefore,the coating 120 can be prepared with a relatively high water-cementratio (e.g., greater than 0.7; or within the range of 0.78 to 0.82) suchthat the reaction between water and cement in the cementitious mixtureyields excess water as the coating 120, thereby resulting in the coating120 exhibiting a highly porous microstructure that is permeable towater, therefore resulting in greater moisture flux through theresulting heatsink 102.

For example, the coating 120 can define a cementitious mixture of waterand calcium silicate cement mixed at a water-cement ratio between 0.8and 1.0 to achieve high porosity and increase hydrophilic tendencies ofthe coating 120.

Furthermore, the coating 120 defines a void network 121 configured tofilter hydrophobic molecules and increase the hydrophilicity of thecoating 120 and thereby the heatsink 102. The coating 120 can define thevoid network 121 including: micropores that wick water through thecoating 120, and that exhibit a first size smaller than pores in thenetwork of pores 112; and nanopores that are hydrated at standardconditions (e.g.,) to increase the hydrophilicity of the coating 120,and that exhibit a second size smaller than the first size such thatlarger hydrophobic molecules cannot displace water in the hydratednanopores. The coating 120—defining this void network 121—lines thenetwork of pores 112 of the substrate 110 to wick moisture through thecoating 120 while larger pores in the network of pores 112 provide anincreased heat exchange surface and enable airflow through the heatsink102.

7.1 Coating Additives

As shown in FIG. 1, the coating 120 lines each surface of the substrate110 and walls of the network of pores within the substrate 110. In onevariation, the coating 120 includes an additive that reduces viscosityof the cementitious mixture such that the cementitious mixture can fullycover and wet external surfaces of the substrate 110 and walls of theinternal network of pores within the substrate 110. For example, thecoating 120 can include superplasticizers that increase fluidity of thecementitious mixture. Additionally or alternatively, the coating 120 caninclude surfactants that lower surface tension and therefore increasefluidity of the cementitious mixture.

As shown in FIG. 1, the coating 120 lines each surface of the substrate110 and walls of the network of pores within the substrate 110 to form ahydrophilic, highly-permeable porous structure (e.g., the heatsink 102).In one variation, the coating 120 includes aggregates that increasehydrophilicity of the coating 120. For example, the coating 120 caninclude Silica Fume aggregates that increases the resistanthydrophilicity of the coating 120 and therefore increases a rate ofmoisture wicking through the resulting heatsink 102.

Additionally and/or alternatively, cement colorants may be added to themixture of water and cement. These cement colorants can be added to thecoating 120 at concentrations ranging from three percent to ten-percentof the weight of the coating 120. The addition of cement colorants tothe coating 120 can enable detection of defects in the coating 120 suchas chips, breaks, fractures, etc. For example, the coating 120 caninclude a cement colorant corresponding to particular pigment. Afterapplication of the coating 120 on the substrate 110, the coating 120cures on surfaces of the substrate. The pigment, defined by the cementcolorant, may collect or separate on these surfaces to reveal fracturesin the coating 120. The addition of cement colorants to the coating 120can also enable detection of salt and/or dirt present on surfaces of theheatsink 102. For example, the coating 120 can include a cement colorantcorresponding to a red pigment. As salt collects on surfaces of theheatsink 102 from skin of a user sweating while wearing the dermalheatsink 102, the heatsink may require cleaning by the user to removesalt and/or other contaminants. In this example, the pigment of the saltis distinct from the pigment of the coating 120. Therefore, the user mayeasily see that the dermal heatsink is dirty (e.g., collecting salt) andrequires cleaning. In another example, a high contrast of the pigmentfrom the color of substrate may indicate to a user to dispose of orreplace the dermal heatsink 100. Alternatively, no cement colorants maybe added to the mixture of water and cement. For example, a whitecoating may be mixed from Portland white cement and water. The coating120 may be left white in order to reflect a maximum amount of light,thereby increasing the cooling effect of the dermal heatsink 100 whenworn by a user.

8. Substrate Fabrication

Block S110 of the method S100 recites fabricating the substrate. Inparticular, in Block S110, the substrate 110 can be fabricated to form abase 118 defining and a set of fins 9 extending from the base 18. Forexample, the substrate 110 can define a rectangular base with a row ofrectangular fins or a grid array of square fins (shown in FIGS. 1A and1B) extending upwardly from the rectangular base. In another example,the substrate 110 includes: a base defining a polygonal cross-sectionaccording to a cell in a Voronoi pattern; and a set of fins arranged ina row, grid array, or nested Voronoi pattern and extending upwardly fromthe base.

In one implementation, the substrate 110 is fabricated by machining aporous, thermally-conductive material. In one example, the substrate 110is machined from a block of graphite foam. In this example, the block ofgraphite foam can define a material exhibiting: relatively high thermalconductivity compared to common metal conductors (e.g., copper); a lowdensity (e.g., less than 0.6 g/cm³); and relatively uniform pore size(e.g., approximately between 0.8 and 1.6 millimeters) such that air mayflow through these pores. In another example, graphite powder can beprinted, injection-molded, sintered, and/or cast to form the substrate110.

In a similar example, the substrate 110 is fabricated from porousgraphite defining the open network of pores 112. The open network ofpores 112 exhibits pore size less than 1.5 millimeters such that whenthe coating 120 is later applied to the substrate 110 and an excesscoating is removed, the open network of pores 112 exhibits an effectivepore size less than 1.2 millimeters through the heatsink 102. However,the substrate 110 can be formed in any other way and in any othergeometry.

9. Substrate Preparation

The substrate 110 can then be cleaned to remove oils and othercontaminants. For example, the substrate 110 can be cleaned with a setof solvents by rinsing the substrate 110 with these solvents or byimplementing an ultrasonic cleaning process for approximately fifteenminutes. Solvents in the set of solvents can include: acetone, isopropylalcohol, ethanol, and other solvents. After cleaning the substrate 110with the set of solvents, the substrate 110 can be dried. In onevariation, the substrate 110 may be rinsed with distilled water toremove solvents from the surfaces and pores of the substrate 110 beforethe substrate 110 is dried.

Initially, surfaces of the substrate 110 and walls of the open networkof pores 112 may exhibit low compatibility (e.g., may not react or bond)with the coating 120. Therefore, the surfaces of the substrate 110 canbe functionalized to increase a presence of hydrophilic functionalgroups on these surfaces, such that the coating 120 (e.g., thecementitious mixture) may exhibit stronger bonds with the surfaces ofthe substrate 110 via hydroxide ions of the coating 120 and hydrophilicfunctional groups on these surfaces. The surfaces of the substrate 110can be oxidized to increase compatibility between the substrate 110 andthe coating 120. Additionally or alternatively, surfaces of thesubstrate 110 can be etched to increase surface roughness and thereforeincrease an interface area between the substrate 110 and the coating120.

10. Substrate Activation

Block S120 of the method S100 recites activating surfaces of thesubstrate 110 and walls of the open network of pores 112. Generally, achemical or covalent functionalization process is applied to thesubstrate 110 in order to create defects in surfaces of the substrate110 to increase an interface area between the substrate 110 and thecoating 120.

In one implementation, the heatsink 102 includes a substrate 110defining a graphite foam and is oxidized via application of an electricpotential to the substrate 110 while immersed in a liquid bath. Forexample, the substrate 110 can be submerged in a dilute acid bath (e.g.,a sulfuric acid bath with concentration 1-gram sulfuric acid/i-Ldistilled water) that acts as an electrolyte solution. The substrate 110can be electrically coupled to an anode inserted into the liquid bathand segregated from the substrate 110. An electric voltage can then beapplied between the substrate 110 and the anode, such as up to anoxidation voltage that yields a target current per-unit surface area ofthe substrate 110 for a preset oxidation duration, such as: between100-miliamps and 400-milliamps per-square-centimeter of surface area ofthe substrate 110 for a period between 10 minutes and 40 minutes.Therefore, surfaces of the substrate 110 can be activated by submergingthe substrate 110 in an aqueous bath and exposing the substrate 110 toan electric potential to: oxidize surfaces of the substrate 110;increase surface roughness of surfaces of the substrate 110; andactivate surfaces of the substrate 110 to bond with functionalhydrophilic groups of the coating 120.

In one variation, multiple substrates are machined into a singlegraphite foam block, such that multiple substrates can be electricallycoupled to the anode and surfaces of the substrates are oxidized via abridge of graphite foam connecting these substrates. At a later time(e.g., after applying the coating 120), the substrates can be separated(e.g., via a CNC drill).

In another implementation, these surfaces of the substrate 110 arewashed with or exposed to surfactants (e.g., sodium dodecyl benzenesulfonate, sodium dodecyl sulfonate) in order to functionalize surfacesof the substrate 110 via a non-covalent functionalization process.

In yet another implementation, these surfaces of the substrate 110 arecoated with a polymer including hydrophilic groups (e.g., polydopamine)in order to functionalize surfaces of the substrate 110 via anon-covalent functionalization process.

11. Coating Application

In a first form (e.g., an aqueous cementitious mixture), the coating 120includes a volume of cement and a volume of water (e.g., distilledwater) mixed at an appropriate ratio (e.g., 0.8 water/cement) such thatthe coating 120 exhibits a viscosity sufficiently low to enable thecoating 120 to flow over the surfaces of the substrate 110 and intopores and channels of the open network of pores 112. The coating 120solution can be mixed separately according to a particular water-cementratio (e.g., 0.8-g water/1-g cement) for approximately one minute via amixer (e.g., impellor, vibrator). In one variation, the coating 120 canbe mixed at a lower water-cement ratio with the addition ofsuperplasticizers to increase fluidity of the cementitious mixture.Additionally and/or alternatively, the cementitious mixture can includesurfactants to lower surface tension and therefore increase fluidity andmaneuverability. Furthermore, the coating 120 can be mixed at lowtemperatures (e.g., five degrees Celsius) such that the cementitiousmixture will react or set more slowly. Cement colorants may also beadded to the cementitious mixture at concentrations ranging fromthree-percent to ten-percent of a weight of the cement.

After mixing the coating 120, the coating 120 is deposited on theactivated surfaces of the substrate 110 including: the interior surface114, the exterior surface 116, and the walls of the open network ofpores 112. In one variation, the substrate 110 can be submerged in thecoating 120 solution and stirred sufficiently (e.g., for approximately10-seconds) such that the coating 120 lines the open network of pores112 of the substrate 110 and both the exterior and interior surfaces 114of the substrate 110. Alternatively, the coating 120 may be sprayed ontothe substrate 110 to line the surfaces of the substrate 110 and walls ofthe open network of pores 112. After the coating 120 is sufficientlyapplied to the substrate 110 (e.g., evenly coating each surface of thesubstrate 110 and walls of the pores), the substrate 110 is removed fromthe cementitious mixture for removal of any excess cementitious mixtureand drying.

Therefore, the heatsink 102 can be formed by applying the coating 120over the substrate 110 including: preparing a mixture of water andcement at a water-cement weight ratio greater than 0.65; agitating themixture (e.g., via a bubbler, impeller, or vibrator); immersing thesubstrate 110 in the mixture; and drying the mixture to form the coating120 defining a heterogenous microstructure permeable to water over theinterior surface 14, the exterior surface 116, and walls of the opennetwork of pores 112.

12. Setting and Pore Cleaning

After the substrate 110 is removed from the cementitious mixture, excesscoating 120 can be driven out of the open network of pores within thesubstrate 110.

In one implementation, after the coating 120 is first applied to thesubstrate 110 and before the coating 120 dries or hardens, positivepressure is applied to the substrate 110 to force excess coating 120from the substrate 110. For example, a jet of compressed area can bewashed over the substrate 110 and the coating 120 to drive any excesscoating through and out of the open network of pores 112. In anotherexample, the interior surface of the substrate 110 is set over andclamped around a bore in a pore-clearing jig, and the bore ispressurized to drive excess coating 120 from the open network of poresin the substrate 110. In this example, the bore can be pressurized withcompressed air, nitrogen, or other inert gas (e.g., up to 5 psi): for apreset duration of time (e.g., 5 psi for one minute); until a gas flux(i.e., a volume flow rate) through the pore-clearing jig and substrate110 exceeds a minimum gas flux corresponding to a maximum obstruction ofpores in the substrate 110 by the coating 120; or until a pressure dropacross the substrate 110 falls below a maximum pressure dropcorresponding to a maximum obstruction of pores in the substrate 110 bythe coating 120.

In another implementation, after the coating 120 is first applied to thesubstrate 110 and before the coating 120 dries or hardens, negativepressure is applied to the substrate 110 to draw excess coating 120 fromthe substrate 110. For example, the interior surface of the substrate110 is set over a bore in a pore-clearing jig, and a vacuum is drawn onthe bore to suction excess coating 120 from the open network of pores inthe substrate 110. In this example, a vacuum can be drawn on the bore:for a preset duration of time (e.g., 250 mmHG for one minute); until agas flux through the pore-clearing jig and substrate 110 exceeds aminimum gas flux corresponding to a maximum obstruction of pores in thesubstrate 110 by the coating 120; or until a pressure drop across thesubstrate 110 falls below a maximum pressure drop corresponding to amaximum obstruction of pores in the substrate 110 by the coating 120.

Furthermore, by applying positive or negative pressure to the substrate110 while the coating 120 on the substrate 110 is still wet, the coating120 can be maneuvered throughout the open network of pores 112 in thesubstrate 110 to contact, coat, and thoroughly line substantially allwalls within the open network of pores 112 in the substrate 110. Activeremoval of excess coating 120 from the substrate 110 can also becontrolled (e.g., by time, gas flux through the substrate 110, and/orpressure change across the substrate 110) in order to achieve a coatingon walls of the internal network of pores in the substrate 110 thatyields: a consistent cross-sectional area of pores through thesubstrate; pores through the substrate that are wide enough to passwater (e.g., human sweat, such as via capillary action); and poresthrough the substrate that are narrow enough to mechanically obstructoils.

Therefore, after cleaning the open network of pores in the substrate 110with positive or negative pressure, a fine and approximately uniformlayer of the coating 120 may remain on walls of the internal network ofpores in the substrate 110.

The coating 120 and the substrate 110 can then set—such as at roomtemperature for preset setting duration (e.g., 24-hours)—such that thecoating 120 sets (e.g., hardens and solidifies) over the substrate 110to form the heatsink 102.

13. Base Layer

In one variation, an additional layer of the coating 120 is applied tothe interior surface 114 of the substrate 110 such that to form athicker base layer configured to contact skin of a user and to bufferthe substrate 110 from impact against the user's body during use. Morespecifically, because the porous material of the substrate 110 may bemore brittle and exhibit a lower modulus of elasticity than the coating120, an additional layer of the coating 120 can be applied over theinterior surface 114 of the substrate 110 in order to form a more robustinterface between the substrate 110 and a user's skin.

For example, an additional layer of the coating 120 can be sprayed ontothe interior surface 114 of the substrate 110 to form a thicker baselayer that is two millimeters thick and that extends internally throughthe open network of pores 112 from the edge of the coated substrate 110by two-millimeters, thereby increasing heat absorption from the userinto the heatsink 102, and increasing mechanical robustness of theheatsink 102.

In one variation, a base layer of the coating 120 is applied over theinternal surface 114 of the substrate 110 after removing an excess ofthe coating 120 from the substrate 110 to fill the open network of pores112 at the base of the substrate 110. For example, an excess of thecoating 120 can be removed from the substrate 110 to render the coating120 of thickness less than 200 microns on walls of the open network ofpores 112 in the substrate 110. After the excess coating 120 is removed,a base layer of the coating of thickness greater than one millimeter canbe deposited on the interior surface 114 of the substrate 110 andpenetrate the open network of pores 112 at a depth of one-millimeter,thereby increasing moisture wicking through the microstructure of thebase layer of the coating 120 and increasing contaminant resistance atthe interior surface of the substrate 110.

14. Hydration

In one variation, after the coating 120 sets (e.g., solidifies) over thesubstrate 110, the coated substrate 110 (hereinafter the “heatsink 102”)is submerged in a water bath (e.g., distilled water bath) to hydrate thecoating 120. While the heatsink 102 is submerged in the water bath, theheatsink 102 is heated from an initial temperature (e.g., ambienttemperature) to a cure target temperature (e.g., greater than 60°Celsius) and held at this cure target over a cure duration (e.g., 72hours; ten days; twenty days).

For example, the heatsink 102 can be submerged in a heated water bath,the heatsink 102 at a first temperature of 20° Celsius. The heatsink 102can then be gradually heated to a second temperature of 70° Celsius overa duration of five days in order to minimize weakening or fractures ofthe coating 120 during this period. The heatsink 102 can remain in thisheated water bath—held at the second temperature—for an additional fivedays to complete the hydration process. At this conclusion of thisten-day hydration process, the heatsink 102 can be removed from thewater bath, cooled, rinsed with distilled water to remove residue of thehydration process, and dried (e.g., by air-drying at room temperature).

In another variation, the heatsink 102 is exposed to a high-humidity,high-temperature environment during the hydration process. For example,the heatsink 102 can be loaded into a humidity chamber, and the humiditychamber can then drive its internal environment to 70° Celsius whilemaintaining its internal humidity at a water vapor saturation pressure(i.e., 100% humidity) over a ramp period (e.g., one day). The humiditychamber can maintain its internal environment under this condition foran additional soak period (e.g., two days) before returning its internalenvironment to ambient conditions during a cool-down period (e.g., fourhours), at which time the hydration process is completed and theheatsink is removed from the humidity chamber.

Therefore, after excess coating 120 is removed from the substrate 110:the resulting heatsink 102 can be immersed in an aqueous bath during acuring period greater than twenty-four hours; the aqueous bath can beheated to a curing temperature over a first duration of the curingperiod (e.g., approximately one-third of the duration of the curingperiod); and the aqueous bath can be held at the curing temperature overa second duration of the curing period in order to hydrate and cure thecoating 120. Following conclusion of the curing period, the heatsink 102can be rinsed and dried.

However, the coating 120 can be hydrated and cured according to anyother schedule or schema.

15. Carbonation & Cleaning

During the hydration process, calcium ions present in the coating 120react with carbon dioxide in the environment to produce calciumcarbonate on surfaces of the coating 120. This calcium carbonate mayincrease mechanical resilience of the coating 120 and therefore increasemechanical resilience of the heatsink 102 as a whole.

However, this calcium carbonate may also decrease porosity of thecoating 120 (e.g., by obstructing a void network 121 of the coating 120)and the heatsink 110 more generally (e.g., by obstructing the voidnetwork 121 of the coating 120). Therefore, the heatsink 102 can beexposed to a decarbonation process to remove excess calcium carbonatefrom the coating 120, thereby increasing porosity of the heatsink 102while maintaining mechanical resilience of the coating 120.

For example, formation of calcium carbonate on the coating 120 appliedover surfaces of the substrate 110 and within the open network of pores112 may increase the mechanical resilience but reduce a porosity of theheatsink 102. To mitigate this reduction in porosity of the heatsink102, the heatsink 102 can be cleaned with an acid (e.g., hydrochloricacid, acetic acid) to remove excess calcium carbonate from the surfaceof the cured coating 120—both on the external surfaces of the heatsink102 and in pores within the open network of pores 112 in the heatsink102.

Furthermore, to increase permeability of the coating 120 itself towater, and thus increase water-carrying capacity of the heatsink 102,the heatsink 102 can be processed to increase carbonation in the coating120 and then processed to remove both superficial calcium carbonate onsurfaces of the coating 120 and to remove calcium carbonate from themicrostructure of the coating 120, thereby introducing a greaterconcentration of pores that are permeable to water within the coating120 and increasing exposure of hydrophilic surfaces of the coating 120.

In one example, following completion of the hydration process describedabove (e.g., after removing the heatsink 102 from the water bath), theheatsink 102 is located in an atmospheric chamber, which is then filledwith a high concentration of carbon dioxide (e.g., 10%, 50%, or 100%carbon dioxide) in order to increase a rate of carbonation (i.e.,formation of calcium carbonate) within the coating 120 as the coating120 continues to cure. After soaking in the carbon dioxide-richenvironment, the heatsink 102 is then removed from the atmosphericchamber and immersed in an acid bath—such as with a high concentrationof hydrochloric acid or acetic acid (e.g., vinegar)—for a short duration(e.g., less than fifteen seconds) to dissolve (or “etch”) calciumcarbonate from both surfaces of the coating 120 and from themicrostructure of the coating 120. Therefore, the heatsink can be:located in a gas environment of a proportion of carbon dioxide greaterthan 10% to promote formation of calcium carbonate in the coating 120;and rinsed with an acid to remove excess calcium carbonate from thecoating 120 along walls of the open network of pores 112 in thesubstrate 110.

Furthermore, carbonation may lower a pH of the coating 120. For example,the coating 120 may exhibit a first pH level (e.g., greater than “9”)following the hydration process; such high pH of a surface in contactwith human skin may result in irritation or chemical burns over a longexposure. Therefore, the heatsink 102 can be carbonated to reduce the pHof the coating 120 to a second pH level—less than the first pH level(e.g., to between “7” and “8”)—such that heatsink may remain in contactwith a user's skin over extended periods of time without irritation tothe user.

16. Increased Hydrophilicity & Resistance

In one variation, the heatsink 102 includes a second layer applied overthe coating 120 and can be configured to increase hydrophilicity andincrease contaminant resistance of the heatsink 102 (or the coating 120more specifically).

In one implementation, a second layer of a methyltrimethoxysilane (or“MTMS”) is applied to the heatsink 102 after carbonation of the coating120 described above. Generally, MTMS may exhibit relatively highcompatibility with aqueous processing environments while exhibitinglower environmental impact than fluorinated materials. Additionally,hydroxyl groups of the MTMS layer can bind the coating material (e.g.,cement or other desiccants) via hydrogen bonds resulting in condensationand formation of permanent siloxane bonds between the coating 120 andthe second MTMS layer. Thus, when applied over the coating 120, thesecond layer of MTMS may increase water uptake (e.g., from a user'sskin) at the contact surface 126 and increase water flow rate throughthe heatsink 102. For example, MTMS (e.g., deposition grade, ≥98%) canbe mixed with 0.1 molar solution of hydrochloric acid at a 4:1 ratio byvolume. This solution can be sonicated in an ice bath for approximatelyfive minutes to induce hydrolysis of the solution. Following thehydration process and/or following the carbonation process describedabove, the heatsink 102 can be immersed in this hydrolyzed MTMS solutionfor a coating duration (e.g., two minutes) in order to coat surfaces ofthe coating 120 with the second layer of MTMS. The heatsink 102 can thenbe removed from the hydrolyzed MTMS solution, rinsed (e.g., in water),and dried. For example, the heatsink 102 can be blown dry withcompressed gas such as described above and then set to dry and cure on adrying rack (e.g., at ambient conditions) for a drying period (e.g., sixhours, twelve hours).

Furthermore, prior to immersing the heatsink 102 in the hydrolyzed MTMSsolution, the heatsink 102 can be cleaned (e.g., with a solvent) toremove oils and other organic compounds from the heatsink 102. Forexample, the heatsink 102 can be rinsed with acetone, methanol, and/orisopropanol. The heatsink can then be exposed to an air plasma forapproximately five minutes in order to remove solvent residue from theheatsink 102 and to increase presence of hydroxyl groups on surfaces ofthe coating 120 to application of the second layer of MTMS.

In other implementations, the contact surface 126 of the heatsink 102 iscoated with a second layer of silver nitrate, silver nitrite, or otherskin-safe metal—such as via electro-plating, chemical vapor depositioncoating, or sputtering, etc.—in order to form a buffer between a user'sskin and the coating 120 and thus reduce possibility of irritation ofthe user's skin by the coating 120 during use. However, a second layerof any other material can be applied to the coating 120 in any other wayin order to increase water uptake and/or reduce skin irritation by theheatsink 102.

17. Silica Gel & Desiccant Structure

In one variation, the hydrophilic coating 120 forms a silica gelstructure. In particular, the substrate 110 defines an open network ofpores 112 exhibiting relatively larger sizes and extending throughout aheatsink 102; and the coating 120 defines a porous, hydrophilicmicrostructure with pores exhibiting relatively smaller sizes and linesinterior and exterior surfaces of the substrate to produce—afterchemical treatment as described above—a robust, hydrated silica gelstructure. To form this hydrated silica gel structure, the coating 120can include a cement-water mixture or other desiccant-water mixtures.

In this variation, the silica gel coating 120 defines a hydrophilicmicrostructure with pores exhibiting relatively smaller sizes includingmicropores of a first size and nanopores (e.g., voids) of a second sizesmaller than the first size. The silica gel coating 120 can be hydratedsuch that the nanopores of the coating 120: are hydrated (e.g., filledwith water) at normal conditions (e.g., 20° C. at 101.325 kPa); aresufficiently small such that larger hydrophobic molecules cannotdisplace water in the nanopores; increase hydrophilicity of the coating120 and thereby the heatsink 102. Further, the silica gel coating can beconfigured such that micropores of the coating 120 are larger than thenanopores of the coating 120 but smaller than pores of the network ofpores 112 such that water freely flows these micropores.

Therefore, the silica gel structure of the coating 120 interacts withthe open network of pores 112 of the substrate 110: to wick water fromskin of a user through the void network 121 of the coating 120; toprevent oils from displacing water molecules in the void network 121;and to enable air and oils to flow through the larger pores of thenetwork of pores 112.

Alternatively, the hydrophilic coating 120 can include: an alumina; azeotype; an aluminophosphate; a metal organic framework; a zinchydrogel; or other desiccants. Because desiccants adsorb water understandard conditions (e.g., 20° C. at 101.325 kPa), the coating 120 maybe hydrated with water and therefore exhibit greater, hydrophilicityunder such conditions. A hydrophilic coating 120 including a desiccantmaterial can define a hydrophilic microstructure with pores exhibitingrelatively smaller sizes including micropores of a first size andnanopores (e.g., voids) of a second size smaller than the first size,similar to the silica gel structure.

Therefore, because the coating 120 includes a silica gel or desiccantmaterial that forms a microstructure of voids of relatively small size(e.g., smaller than pores in the open network of pores 112 of thesubstrate 110), the coating 120 restricts displacement (or“replacement”) of water molecules in voids of the coating 120 bycontaminant molecules (e.g., oils). For example, the coating can includea desiccant forming a void network 121 defining a microstructure ofnanopores exhibiting widths (or diameters) less than 1.0 nanometer suchthat water molecules may fill these voids (or “pores”) and such thatthese voids reject uptake of larger hydrophobic molecules, such as oilsfrom a user's skin.

18. Wearable Heatsink

In one variation, the heatsink 102 is integrated into or connected to atextile to form a wearable heatsink configured to attach to a user or tobe worn by a user and to retain the contact surface 126 of the heatsink102 in contact with the user's skin.

In one implementation, the dermal heatsink 100 includes a textile panel130 defining a first aperture 132; and the heatsink 102 is arranged inthe first aperture 132 with an interior surface 114 of the substrate 110approximately coplanar with the textile panel 130. In thisimplementation, the dermal heatsink 100 further includes a heatsinkretainer 140 bonded to the textile panel 130 about a periphery of thefirst aperture 132 and bonded to a perimeter of the heatsink 102 and/ormechanically retaining the heatsink 102 to the textile panel 130.

18.1 Heatsink Retainer: Polymer Frame

In one implementation, the heatsink 102 attaches to the textile panel130 via a polymer frame encircling the thermally conductive heatsink. Inone variation, the heatsink retainer 140 is a square shaped,thermoplastic polymer. Alternatively, the heatsink retainer 140 can bemachined from aluminum or cement. The heatsink retainer 140 can securelyattach the heatsink 102 to the textile panel 130 and increase themechanical resilience of the heatsink 102. The heatsink retainer 140 canbe adhered to the textile panel 130 by partially melting or injectingthe frame into the textile panel 130 and the heatsink 102. In onevariation, a first heatsink retainer 140 is attached to a perimeter ofan aperture of the textile panel 130 before inserting the heatsink 102into the aperture. Upon insertion of the heatsink 102, a second heatsinkretainer 140 is melted into the perimeter of the heatsink 102 and theperimeter of the aperture to secure the heatsink 102. Additionally, theheatsink retainer 140 can include a set of claws 142 configured toextend between fins of the heatsink 102 for additional security.

18. Multiple Heatsinks

In one implementation, the heatsink 102 can be integrated into a dermalheatsink 100 including multiple heatsinks 102 and defining a headband160 configured to be worn by a user such that the heatsink 102 contactsskin on a forehead of the user. In this example, the dermal heatsink 100can include: a textile panel 130 defining a first aperture 132; aheatsink 102 defining a substrate 110 and a coating, the heatsink 102arranged in the first aperture 132 with an interior surface 114 of thesubstrate 110 approximately coplanar with the textile panel 130; and aheatsink retainer 140 bonded to a perimeter of the heatsink 102 andbonded to the textile panel 130 about a periphery of the first aperture132.

In this implementation, the dermal heatsink 100 can include: a secondheatsink arranged in a second aperture 133 defined by the textile panel130, the second heatsink defining a second substrate and a secondcoating. The second substrate defines: a second interior surface 114configured to thermally couple to a second heat source 150; a secondexterior surface 116; and a second open network of pores extendingbetween the second interior surface 114 and the second exterior surface116. The second coating includes the hydrophilic, contaminant resistantmaterial: extending across the second exterior surface 116 of the secondsubstrate; extending across the second interior surface 114 of thesecond substrate; and lining the second open network of pores within thesecond substrate.

The second heatsink can include a second polymer frame bonded to asecond perimeter of the second heatsink and bonded to the textile panel130 about a second periphery of the second aperture 133. In thisexample, each heatsink and therefore each aperture can be approximatelytwo-inches in length.

A gap between the two heatsinks 102 on the textile panel 130 enables thetextile panel 130 to bend according to the shape of a user's forehead.

To prevent collisions between adjacent heatsinks 102 on the textilepanel 130, polymer frames about adjacent heatsinks 102 are configured tocollide between each other before the heatsinks 102 can collide. Forexample, the plastic frames can be configured to exhibit a certainheight such that a first angle of collision of the polymer frames isless than a second angle of collision of the heatsinks 102.

18.3. Heatsink Pattern

In one implementation, the dermal heatsink 100 is configured to fitaccording to a curvature of a human body. For example, the dermalheatsink 100 can include: a textile vest configured to be worn on ahuman torso and defining a grid array of apertures; and a set ofheatsinks 102, each heatsink in the set of heatsinks 102 retained in anaperture in the set of apertures in the textile panel 130. The set ofheatsinks 102 can be configured to: contact skin on a torso of a userwhen the textile vest is worn by the user; and wick moisture from skinof the torso of the user to cool the user. The grid array of aperturescan be arranged in a pattern such that when the textile vest is worn bythe user, it is flexible about the curvature of the torso of the user.In one variation, the grid array of apertures are arranged according toa Voronoi geometry, such that the dermal heatsink 100 can cover complex3D surfaces (e.g., of the human body) and dissipate heat from the heatsource 150 (e.g., a human body) efficiently. For example, the dermalheatsink 100 can include: a textile vest configured to be worn on ahuman torso and defining a grid array of apertures; and a set ofheatsinks 102 comprising the heatsink 102, each heatsink 102 in the setof heatsinks 102 retained in an aperture in the set of apertures in thetextile vest and arranged in a Voronoi pattern. The set of heatsinks 102can be configured to: contact skin on a torso of a user when the textilevest is worn by the user; and wick moisture from skin of the torso ofthe user to cool the user.

In one variation shown in FIGS. 2A and 2B, the dermal heatsink 100 isconfigured to include heatsinks 102 of varying shape and size such thatthe dermal heatsink conforms to different regions of the body exhibitingdifferent curvature. For example, a dermal heatsink 100 can beconfigured to be worn about a forearm of a user. The dermal heatsink caninclude: a first heatsink of a first size configured to contact skin ona first region of the forearm corresponding to a dorsal side of theforearm; a second heatsink of a second size configured to contact skinon a second region of the forearm corresponding to a side of theforearm, the second size less than the first size. Therefore, heatsinks102 configured to contact skin in regions of the body exhibiting greatercurvature (e.g., the wrist) can be machined to smaller sizes thanheatsinks 102 configured to contact skin in regions of the bodyexhibiting flatter surfaces (e.g., the abdomen) in order to maximize asurface area of skin covered by heatsinks 102 such that heat isdissipated from skin of the user by the heatsink 102 at a higher rate,thus cooling the user more quickly.

18.4 Removable Heatsinks and Textile Panel

In the foregoing implementations, the heatsink 120 is intransientlybonded or coupled to the textile panel 130 (e.g., by the heatsinkretainer 140), which forms a complete article of clothing, such as ashirt, a headband, or an armband. Alternatively, the textile panel130—with integrated heatsink 102—can be configured to transientlyinstall on a garment and to be removed from the garment, such as whenthe garment is washed or to replace the textile panel 130 and heatsink102 with a new unit of the textile panel 130 and integrated heatsink 102when the former is soiled after repeated use. For example, the textilepanel 130—with integrated heatsink 102—can include snaps or buttonsconfigured to attach or engage to corresponding features on a shirt orother garment. In another example, the textile panel 130—with integratedheatsink 102—can be configured to transiently couple to an article ofclothing via a hook and loop fastener or a zip fastener.

In another implementation, the heatsink retainer 140 is configured totransiently retain an individual heatsink 102 to the textile panel 130,thereby enabling the individual heatsink 102 to be removed from thetextile panel 130 when a garment containing the textile panel is washedor when the heatsink 102 is replaced with a new heatsink 102. Forexample, the set of claws 132 in the heatsink retainer 140 can beretractable to release the heatsink from the heatsink retainer 140.

However, the heatsink 102 can be transiently or intransiently coupled tothe textile panel 130 in any other way, and the textile panel 130 canform directly or can be transiently coupled to a garment in any otherway and in any other format.

19. Dermal Heatsink Examples

In the foregoing variation, the textile panel 130 can form or can beintegrated into the dermal heatsink 100 configured to be worn by a userand to retain a set of heatsink 102 in contact with the user's skin. Forexample, the dermal heatsink 100 can define a textile or clothingarticle including: a cap; a shoe; a helmet; a shirt; a vest; a headband;a wristband; an armband; or protective gear; etc.

19.1 Example: High Sweat Rate Areas

In one variation, the dermal heatsink 100 includes a cluster or group ofheatsinks 102 and is configured to locate these heatsinks 102 in aregion of a human body associated with a relatively high sweat rate(e.g., where sweating by a human body is commonly most profuse) in orderto achieve a consistent, high rate of heat dissipation from a user'sbody during intensive exercise or activity by the user. For example, inthis variation, the dermal heatsink 100 can be configured to locate acluster of heatsinks 102 on a region of the human body typicallycontaining a relatively high density of sweat glands and/or containing arelatively high density of superficial veins proximal the surface of theskin.

For example, a dermal heatsink can be configured to be worn across anabdomen of a human user. In this example, the dermal heatsink caninclude: a first set of heatsinks 102 exhibiting a first total area ofcontact surfaces 126 configured to contact the user's skin on a dorsalregion of the abdomen; and a second set of heatsinks 102 exhibiting asecond total area—less than the first total area—of contact surfaces 126configured to contact skin on a side region flanking the user's abdomen.In this example, because the user's abdomen may produce a higher volumeof sweat due to the higher density of sweat glands in this region of thebody, the second set of heatsinks 102 located over the user's flank mayspan a smaller surface area of the user's body than the first set ofheatsinks 102 located over the user's abdomen. Therefore, the dermalheatsink 100 may locate more heatsinks 102 in regions of the user's bodyat which more sweat is produced in order to maintain high thermalextraction efficiency (i.e., “cooling”) of the user; and vice versa inorder to limit complexity of the dermal heatsink 100.

The dermal heatsink 100 can define a headband configured to be wornacross the forehead of a human user. For example, the dermal heatsink100 can define: a textile panel of rectangular shape of a length lessthan ten inches and a width less than three inches; a set of heatsinks102 arranged in a row within the textile panel, such that heatsinks inthe set of heatsinks 102 contact skin on a human user's forehead. Thetextile panel can be incorporated into a headband (via laser cutting orsewing techniques) such that the headband may be worn about a humanuser's head, and the textile panel including the row of heatsinks 102contacts skin of the human user's forehead when the headband is worn. Inthis example, a user's head including the forehead may produce a highvolume of sweat due to the higher density of sweat glands in this regionof the body, however, a back side of the head may produce less sweatabsorbable by the heatsinks 102 due to hair from the head decreasingcontact between the heatsinks 102 and skin on the head of the user.Therefore, the dermal heatsink 100 may locate more heatsinks 102 on aportion of the headband in contact with the forehead of the user.

The dermal heatsink 100 can define a vest configured to be worn on ahuman torso. For example, the vest can include: a textile panel defininga textile vest configured to be worn on a torso of a human user and aset of apertures; a first grid array of heatsinks 102 including a firstquantity of heatsinks, each heatsink in the first grid array ofheatsinks 102 retained in an aperture in the set of apertures such thateach heatsink in the first grid array of heatsinks 102 contacts skin ona chest of a human user wearing the vest; a second grid array ofheatsinks 102 including a second quantity of heatsinks 102, the secondquantity less than the first quantity of heatsinks 102, each heatsink102 in the second grid array of heatsinks 102 retained in an aperture inthe set of apertures such that each heatsink 102 in the second gridarray of heatsinks 102 contacts skin on a lateral torso of a human userwearing the vest. Therefore, in this example, the vest locates a higherquantity of heatsinks 102 at a chest region of the human body than at alateral region of the human body, as a greater volume of sweat may beproduced at the chest region than the lateral region.

The dermal heatsink 100 can define a glove configured to be worn over ahuman hand. For example, the dermal heatsink 100 can define: a textilepanel exhibiting a square shape of side lengths less than three inchessuch that the textile panel fits approximately within a palm of a humanuser; a set of four heatsinks 102 arranged in a square pattern withinthe textile panel, such that each heatsink 102 contacts skin on the palmof the user. The textile panel can be incorporated into a glove (vialaser cutting or sewing techniques) such that the glove may be worn overa human user's hand. In this example, the glove locates heatsinks 102within the glove at the palmar side of the hand rather than at thedorsal side of the hand, due to the higher density of sweat glands inthe palmar region than the dorsal region of the hand.

19.2 Example: High-Impact Areas

In one variation, the dermal heatsink 100 is configured to locate acluster of heatsinks 102 over a region of a human body where possibilityof impact in low in order to limit damage to the dermal heatsink 100during use and thus maintain a high and consistent rate of cooling for auser over time. For example, a first dermal heatsink 100 designated fora runner can be configured to locate a duster of heatsinks 102 incontact with skin on the runner's forehead; and a second dermal heatsink100 designated for a soccer player can be configured to locate a dusterof heatsinks 102 in contact with the player's abdomen, which mayexperience less impact than the player's forehead and chest.

19.3 Example: Medical Garment

In one implementation, the dermal heatsink 100 can be worn or attachedto a user for medical purposes. For example, the dermal heatsink 100 canattach or be worn on the forehead (e.g., in a headband 160) of a userexhibiting a fever (e.g., higher than normal body temperature) torapidly cool the body temperature of a user to a normal temperature(e.g., 98.6° Fahrenheit). The user may wet or drench the heatsink 102before attaching the dermal heatsink to her body such that heat transferfrom her skin to the heatsink 102 occurs immediately upon attaching thedermal heatsink.

In another example, a set of heatsinks 102 are incorporated into atextile panel 130 to define a dermal heatsink 100 in the form of a vest.In this example, a patient exhibiting a high fever may wear the vest toreduce a body temperature of the user. The patient or medical staff maydouse the vest with water to increase a rate of cooling. In particular,due to minimal airflow through the vest, the vest can be paired with afan to further increase the rate of cooling such that the bodytemperature of the patient decreases at a high rate.

19.4 Example: Athletic Gear

In one variation, the dermal heatsink 100 is incorporated into athleticgear (e.g., sports uniforms). For example, the dermal heatsink 100 canbe configured to be worn in the sole of a cleat for baseball players. Inanother example, as shown in FIG. 3B, the dermal heatsink 100 can definea visor. In this example, the heatsinks 102 can be permanently attachedto the visor via the heatsink retainer 140 and the set of claws 132. Inyet another example, the dermal heatsink can be configured to be worn ona chest guard or underneath a chest guard of a football player. In thisexample, shown in FIG. 3C, the dermal heatsink 100 can be configured tocontact a chest of the user and exhibit a shape that naturally fits thecurvature of the human chest. Therefore, a perimeter of the dermalheatsink configured to be worn on the chest can exhibit a particularshape distinct from an outline of the dermal heatsink configured to beworn on the forehead of the user. Additionally, the shape and size ofeach individual heatsink 102 may vary according to the curvature of thechest as opposed to that of the forehead. In another example, the dermalheatsink 100 can be configured to be worn on the forearms of a user, asshown in FIG. 3D. In this example, the heatsinks 102 can be configuredto contact skin of the user where sweating is most abundant, such as onthe ventral side of the forearm which typically produces more sweat thanon the dorsal side of the forearm. Additionally, by locating theheatsinks 102 on the ventral side of the forearm, the heatsinks 102 maybe less likely to experience contact or impact from an external source,and therefore may depreciate more slowly.

19.5 Example: Daily Apparel

In one variation, the dermal heatsink 100 is incorporated into apparelworn outside of exercise for everyday wearing by a user. For example,the dermal heatsink 100 can be configured to attach to a collar of ashirt, such that the dermal heatsink is not visible on an exterior ofthe shirt and a user may wear the dermal heatsink to wick sweat aroundthe neck region and to stay cool. In this example, the dermal heatsink100 can be removable such that it is transferable between differentitems of clothing via a set of fasteners, such as a hook and loopfastener.

To increase a rate of cooling, the user may drench the dermal heatsink100 with liquid prior to and/or during use. The heatsink 102 can absorbbody heat from the user in order to evaporate this liquid. Therefore,the apparatus can dissipate heat from the user or heat source 150 in theabsence of sweat and/or physical activity by the user. In one variation,the dermal heatsink 100 includes a liquid reserve configured todistribute liquid to the heatsink 102 passively or actively by the user.Alternatively, liquid can be applied to the heatsink 102 via capsules ofa saturated high absorbent material (e.g., a polyurethane sponge) or viaan external source (e.g., a hose).

19.6 Example: Mechanical Equipment

In one variation, the dermal heatsink 100 is incorporated into machineryto cool parts of a machine that may produce heat when in use. Theheatsink 102 can be scaled appropriately to cool both small-scale andlarge-scale machinery including: portable electronics, computers,motors, cooling towers, chillers, heat exchangers, etc.

For example, the heatsink 102 can be configured to attach to a surfaceof a computer, such that heatsink does not interfere with regular use ofthe computer. In this example, the heatsink 102 can be removable suchthat it is transferable between different devices or the heatsink 102can be rigidly attached to a surface of the computer. The heatsink 102can absorb heat generated by the computer, thereby regulating thetemperature of the computer such that the computer does not overheat.

20. Variation: Direct-to-Body Attachment

In one variation, the textile panel 130 defines a thin layer of flexiblesilicone that can be directly adhered to human skin via an adhesive. Forexample, the dermal heatsink 100 can include: a thin layer of flexiblesilicone defining a set of apertures; an epoxy layer applied to an innersurface of the thin layer of flexible silicone, the inner surfaceapproximately coplanar with the interior surface 112 of the substrate110. In this example, the dermal heatsink 100 can be adhered directly tohuman skin by applying the inner surface of the thin layer of flexiblesilicone to human skin, such that interior surfaces 112 of the heatsinks102 contact skin of the user. Therefore, the dermal heatsink 100 can belocated at different regions of the human body to dissipate heat fromthe user or heat source 150, and is not limited to a particular regionof the human body.

21. Metal Substrate

In one implementation, the substrate 110 is molded from a metallicmaterial, such as aluminum or copper. In this implementation, thesubstrate 110 can be molded to fit a particular size and geometry. Thenetwork of pores 112 can be machined or carved into this metallicsubstrate.

In this implementation, the substrate 110 is cleaned with a set ofsolvents and layer of oxide is formed on surfaces of the substrate 110.To further functionalize surfaces of the substrate 110 before applyingthe coating 120, a mixture of hydrochloric acid and sodium hydroxide canbe used to etch the surfaces of a metal substrate via submersion of thesubstrate 110 in an acid bath. For example, a metal substrate (e.g.,aluminum substrate) can be submerged in an aqueous solution of 5-wt %sodium hydroxide for approximately 120-seconds. The substrate 110 isthen removed from the sodium hydroxide solution and submerged in a 3-wt% hydrochloric acid for approximately 300-seconds at 40° Celsius.Finally, the substrate 110 can be removed from the hydrochloric acidsolution and submerged again in the sodium hydroxide solution for300-seconds. In one variation, for a copper substrate, the substrate 110can be further oxidized by submerging the substrate 110 in a nitric acidbath to achieve further oxidation.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the embodiments of the invention without departing fromthe scope of this invention as defined in the following claims.

I claim:
 1. A method for fabricating a dermal heatsink comprising:fabricating a substrate defining: an interior surface; an exteriorsurface opposite the interior surface; and an open network of poresextending between the interior surface and the exterior surface;activating surfaces of the substrate and walls of the open network ofpores; applying a coating over the substrate to form a heatsink, thecoating comprising a porous, hydrophilic material and defining a voidnetwork; removing an excess of the coating from the substrate to clearblockages within the open network of pores by the coating; hydrating theheatsink during a curing period; and heating the heatsink during thecuring period to increase porosity of the coating applied over surfacesof the substrate; and rinsing the heatsink with an acid to decarbonatethe coating along walls of the open network of pores in the substrate.2. The method of claim 1, wherein activating surfaces of the substrateand walls of the open network of pores comprises: submerging thesubstrate in an aqueous bath; and exposing the substrate to an electricpotential to oxidize surfaces of the substrate, increase surfaceroughness of surfaces of the substrate, and activate surfaces of thesubstrate to bond with functional hydrophilic groups of the coating. 3.The method of claim 1, wherein applying the coating over the substratecomprises: preparing a mixture of water and cement at a volumetricwater-cement ratio greater than 0.65; agitating the mixture; immersingthe substrate in the mixture; and setting the mixture to form thecoating defining a heterogeneous microstructure permeable to water overthe interior surface, the exterior surface, and walls of the opennetwork of pores within the substrate.
 4. The method of claim 1: whereinfabricating the substrate comprises fabricating the substrate fromporous graphite defining the open network of pores of pore sizeapproximately between 0.8 millimeters and 1.6 millimeters; whereinremoving the excess of the coating from the substrate comprises removingthe excess of the coating from the substrate to render the coating ofthickness less than 200 microns on walls of the open network of pores inthe substrate; and further comprising depositing a base layer of thecoating over the interior surface of the substrate and extending adistance greater than one millimeter into the substrate to form a bufferbetween the interior surface of the substrate and skin of a user incontact with the heatsink.
 5. The method of claim 1: wherein hydratingthe heatsink during the curing period comprises immersing the heatsinkin an aqueous bath during the curing period greater than twenty-fourhours; wherein heating the heatsink during the curing period comprises:heating the heatsink to a curing temperature in an aqueous bath over afirst duration of the curing period; and holding the heatsink at thecuring temperature in the aqueous bath over a second duration of thecuring period; and further comprising, in response to conclusion of thecuring period, setting the heatsink.
 6. The method of claim 1, furthercomprising: locating the heatsink in gas environment comprising aproportion of carbon dioxide greater than 10% to promote formation ofcalcium carbonate in the coating; and rinsing the heatsink with an acidto remove excess calcium carbonate from the coating along walls of theopen network of pores in the substrate.
 7. The method of claim 1,further comprising: forming a first aperture in a textile panel;locating the heatsink within the first aperture in the textile panel;locating a heatsink retainer about a periphery of the first aperture inthe textile panel, the heatsink retainer defining a set of clawsextending over channels defined by the heatsink; and bonding theheatsink retainer the textile panel about a periphery of the firstaperture, the set of claws securing the heatsink within the firstaperture.
 8. The method of claim 7: further comprising forming thetextile panel into a headband configured to be worn on a human forehead;wherein forming the first aperture in the textile panel comprisescutting the first aperture exhibiting a first length, corresponding to afirst curvature on the human forehead, in the textile panel; and furthercomprising: cutting a second aperture in the textile panel, the secondaperture exhibiting a second length corresponding to a second curvatureon the human forehead, the second curvature greater than the firstcurvature, and the second length less than the first length; andlocating a second heatsink within the second aperture in the textilepanel; locating a second heatsink retainer about a periphery of thesecond aperture in the textile panel; and bonding the second heatsinkretainer the textile panel about a periphery of the second aperture.